Mineral oil base lubricant



nited States Patent MINERAL OIL BASE LUBRICANT Wilhelm Dietrich, Hans-Joachim Mertens, and Fritz Wetter, Marl, Westphalia, Germany, assignors to Chemische Werke Huls Aktiengesellschaft, a corporation of Germany No Drawing. Application October 12, 1953, Serial No. 385,666

2 Claims. (Cl. 252-475) This invention relates to, extreme pressure lubricants comprising mineral oil bases with additions of organic nitro compounds and sulfurized low molecular weight, aromatic substituted olefines.

In our application Serial No. 372,394, filed August 4, 1953, we have disclosed the improvement of the extreme pressure lubricating properties of mineral oil base lubricants by the addition thereto of organic nitro compounds and oil soluble di and polysulfides of xanthogenates.

We have now found that the extreme pressure lubricity of mineral oils, both natural and synthetic, may be greatly improved by additions of organic nitro compounds and sulfurized low molecular weight aromatic substituted olefines. The sulfurized compound may be either soluble in the mineral oil directly or capable of being brought into solution therein with the aid of a mutual solvent. Under the term mineral oil we mean to include not only the natural and synthetic fluid oils but also the corresponding semi solid or solid greases.

The following are illustrative examples of organic nitro compounds suitable for use in the lubricant compositions; m-dinitrobenzol, bromdinitrobenzol, chlornitrobenzol and ,B-dinitrophenol, and their c-alkyl derivatives and mixtures thereof and other nitro compounds such as nitroparaffines, nitronaphthalenes, and nitronaphthols, this listing being merely illustrative and not limitative.

The sulfurized low molecular weight olefines containing an aromatic residue are compounds which when derived from monoolefines may be represented by the general formula In the above formulae R1 stands for an aryl or aralkyl residue, R2 stands for hydrogen or an aryl, aralkyl or heterocyclic residue, m is 0, 1 or 2 and n is 1 or 2. As appears from these formulae the monoolefines may contain from 2 to 6 carbon atoms and the diolefines may contain from 4 to 10 carbon atoms and the number of sulfur atoms in the molecule may vary from 1 to 2 in the moloolefine compounds and from 2 to 4 in the diolefine compounds. The percentage of sulfur in the molecule will of course depend upon the Weights of the R1 and R2 values.

The sulfurized low molecular weight olefines containing an aromatic residue may be prepared by heating a mixture consisting of a low molecular weight olefine containing an aromatic residue and sulfur in the molecular proportions of about 1:1 at elevated temperatures, below the boiling point of the said olefine, from about 150 to 200 C. for several hours, i. e. 10-15 hours. By employing lower boiling olefines the heating may be effected in an 2,793,999 7 Pe ms M y 8 autoclave under pressure. The unreacted sulfur may be filtered off, whereas the unreacted .olefine will be removed by distillation. Typical examples of compounds which when sulfurized give compounds according to the above formulae are styrene, stilbene, monophenylbutadiene, di-phenylbutadiene, mononaphthylbutadiene, and dinaphthylbutadiene.

Illustrative typical examples of suitable solvents are 2- ethylhexanol, 2-ethyl-l,3-hexanediol, 2-methylpentanediol- 1,4-diethyleneglycol monoethyl ether and diethylene glycol monobutyl ether.

The sulfurized aromatic substituted olefines are made in the well known way by reacting the aromatic substituted olefines with sulfur at elevated temperature.

The amounts of the organic nitro compound and of the sulfurized aromatic substituted low molecular weight ole fine and the particular compounds to be used depends upon the purpose for which the lubricant is to be used. In general the nitro compound addition is only a small fraction of the addition of sulfurized compound e. g. up to about one-tenth, and the addition of the sulfurized compound for the production of extreme pressure lubricants generally is within the range from 0.5% to 10% calculated on the weight of the mineral oil.

The new lubricants containing the additions of nitro compounds and sulfurized compounds exhibit no corrosive effect on metals at normal temperatures as determined by loss in weight and only insignificant corrosive effect at elevated temperatures and long periods of action.

Other additions to the lubricants may be made such as for further improving the extreme pressure lubricity, viscosity, solidifying point, resistance to foaming, resistance to oxidation, etc.

Lubricants, when tested for extreme pressure lubricating properties by means of the customary four ball testing apparatus (FBTA) and method described in the publicat-ion Ol und Kohle, 1944, pages 19-23, and having additions of for example 0.1 to 0.25 percent of organic nitro compound and 1 to 2.5 percent of the sulfurized aromatic substituted lower olefines, permit a loading of from 400 to 1000 kg. before welding of the balls occurs.

It has already been proposed to add nitro compounds and sulfur or sulfurized mineral oils to lubricants but such additions do not give particularly high FBTA values and the results are not readily reproducable whereas the sulfurized aromatic substituted lower olefines, being definite chemical compounds give superior FBTA values and the results are readily reproducable.

The invention is further illustrated by the following specific example. 1 v

To a gear oil having a FBTA number of (density d15/4=0.9320, viscosity at 20 C. -226 E. and 50 C. =22.5 E., viscosity index=l3, solidifying point=13 C.) was added 5% of a sulfurized styrene produced by reacting styrene with sulfur at elevated temperature and having a sulfur content of 23.5%. The resulting lubricant had a FBTA number of 480. By the addition of 0.25% of dinitrophenol to the mixture the FBTA value was raised to 650 whereas the addition of dinitrophenol alone did not give any increase in the FBTA value.

We claim:

1. A lubricant consisting essentially of a lubricating medium selected from the group consisting of mineral oils and greases, a nitro compound selected from the group consisting of aliphatic and aromatic nitro compounds in the range from 0.05 to 1% by weight and a sulfurized low molecular weight aromatic substituted olefine in the range from 0.5 to 10% by weight, both additions being calculated on the weight of the pure lubricating medium, said sulfurized low molecular weight aromatic 3 4 substituted olefine being a compound of the group of residues, m is an integer from 0 to 2 and n is an integer the formulae from 1 to 2.

2. A lubricant as defined in claim 1 in which the sulfurized low molecular weight aromatic substituted ole- 5 fine is a sulfurized member of the group consisting of and styrene, stilbene, monophenylbutadiene, diphenylbuta- R1-(c)..-0\-/-G- 0)...C0-(c),,,-R, diene, mononaphthylbutadiene and dinaphthylbutadiene.

s (s References Cited in the file of this patent 1n which R1 1s a member of the group consistlng of aryl 10 and aralkyl residues, R2 is a member of the group con- UNITED STATES PATENTS sisting of hydrogen and aryl, aralkyl and heterocyclic 2,094;097 Downing et a1 Sept. 28, 1937 

1. A LUBRICANT CONSISTING ESSENTIALLY OF A LUBRICATING MEDIUM SELECTED FROM THE GROUP CONSISTING OF MINERAL OILS AND GREASES, A NITRO COMPOUND SELECTED FROM THE GROUP CONSISTING OF ALIPHATIC AND AROMATIC NITRO COMPOUNDS IN THE RANGE FROM 0.05 TO 1% BY WEIGHT AND A SULFURIZED LOW MOLECULAR WEIGHT AROMATIC SUBSTITUTED OLEFINE IN THE RANGE FROM 0.5 TO 10% BY WEIGHT, BOTH ADDITIONS BEING CALCULATED ON THE WEIGHT OF THE PURE LUBRICATING MEDIUM, SAID SULFURIZED LOW MOLECULAR WEIGHT AROMATIC SUBSTITUTED OLEFIN BEING A COMPOUND OF THE GROUP OF THE FORMULAE 